package com.chexiehui.jc.widget;

import android.content.Context;
import android.support.design.widget.AppBarLayout;
import android.support.design.widget.CoordinatorLayout;
import android.support.v7.widget.RecyclerView;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.widget.LinearLayout;
import android.widget.OverScroller;

import com.chexiehui.jc.R;

import java.lang.reflect.Field;

public class AppBar2Behavior extends AppBarLayout.Behavior {

    private int maxScrollH = 0;
    private int recyclerViewH = 0;

    public AppBar2Behavior() {
        super();
    }

    public AppBar2Behavior(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    @Override
    public boolean setTopAndBottomOffset(int offset) {
        // 重写此方法，判断offset是否超过了最大的可滑动距离，如果超过就不再滑动
        if (maxScrollH <= Math.abs(offset)) {
            offset = -maxScrollH;
        }
        return super.setTopAndBottomOffset(offset);
    }

    @Override
    public boolean onTouchEvent(CoordinatorLayout parent, AppBarLayout child, MotionEvent ev) {

        return super.onTouchEvent(parent, child, ev);
    }

    @Override
    public boolean onMeasureChild(CoordinatorLayout parent, AppBarLayout child, int parentWidthMeasureSpec, int widthUsed, int parentHeightMeasureSpec, int heightUsed) {

        return super.onMeasureChild(parent, child, parentWidthMeasureSpec, widthUsed, parentHeightMeasureSpec, heightUsed);
    }

    @Override
    public boolean onLayoutChild(CoordinatorLayout parent, AppBarLayout abl, int layoutDirection) {
        calculateMaxScrollH(parent, abl);
        return super.onLayoutChild(parent, abl, layoutDirection);
    }
    // 计算最大的可滑动距离
    private void calculateMaxScrollH(CoordinatorLayout parent, AppBarLayout child) {
        RecyclerView recyclerView = parent.findViewById(R.id.recycler);
        LinearLayout ll_all_tip_container = parent.findViewById(R.id.ll_all_tip_container);
        int parentH = parent.getMeasuredHeight();
        /**
         * 获取AppBarLayout可滑动的最大值，得到的值：AppBarLayout的高度去掉悬浮的那块高度
         * 正好可以保证AppBarLayout完全隐藏掉并且悬浮布局显示
         */
        int childScrollTotalH = child.getTotalScrollRange();

        recyclerViewH = recyclerView.getMeasuredHeight();
        // 最大可滑动距离就是AppBarLayout的高度 + 悬浮布局高度 + recyclerView的高度 - parentH
        maxScrollH = childScrollTotalH - parentH + recyclerViewH + ll_all_tip_container.getMeasuredHeight();
        if (maxScrollH < 0) {
            maxScrollH = 0;
        }
    }

    private static final int TYPE_FLING = 1;

    private boolean isFlinging;
    private boolean shouldBlockNestedScroll;

    @Override
    public boolean onInterceptTouchEvent(CoordinatorLayout parent, AppBarLayout child, MotionEvent ev) {
        shouldBlockNestedScroll = false;
        if (isFlinging) {
            shouldBlockNestedScroll = true;
        }

        switch (ev.getActionMasked()) {
            case MotionEvent.ACTION_DOWN:
                stopAppbarLayoutFling(child);  //手指触摸屏幕的时候停止fling事件
                break;
        }

        return super.onInterceptTouchEvent(parent, child, ev);
    }

    /**
     * 反射获取私有的flingRunnable 属性，考虑support 28以后变量名修改的问题
     *
     * @return Field
     */
    private Field getFlingRunnableField() throws NoSuchFieldException {
        try {
            // support design 27及以下版本
            Class<?> headerBehaviorType = this.getClass().getSuperclass().getSuperclass();
            return headerBehaviorType.getDeclaredField("mFlingRunnable");
        } catch (NoSuchFieldException e) {
            // 可能是28及以上版本
            Class<?> headerBehaviorType = this.getClass().getSuperclass().getSuperclass().getSuperclass();
            return headerBehaviorType.getDeclaredField("flingRunnable");
        }
    }

    /**
     * 反射获取私有的scroller 属性，考虑support 28以后变量名修改的问题
     *
     * @return Field
     */
    private Field getScrollerField() throws NoSuchFieldException {
        try {
            // support design 27及以下版本
            Class<?> headerBehaviorType = this.getClass().getSuperclass().getSuperclass();
            return headerBehaviorType.getDeclaredField("mScroller");
        } catch (NoSuchFieldException e) {
            // 可能是28及以上版本
            Class<?> headerBehaviorType = this.getClass().getSuperclass().getSuperclass().getSuperclass();
            return headerBehaviorType.getDeclaredField("scroller");
        }
    }

    /**
     * 停止appbarLayout的fling事件
     *
     * @param appBarLayout
     */
    private void stopAppbarLayoutFling(AppBarLayout appBarLayout) {
        //通过反射拿到HeaderBehavior中的flingRunnable变量
        try {
            Field flingRunnableField = getFlingRunnableField();
            Field scrollerField = getScrollerField();
            flingRunnableField.setAccessible(true);
            scrollerField.setAccessible(true);

            Runnable flingRunnable = (Runnable) flingRunnableField.get(this);
            OverScroller overScroller = (OverScroller) scrollerField.get(this);
            if (flingRunnable != null) {
                appBarLayout.removeCallbacks(flingRunnable);
                flingRunnableField.set(this, null);
            }
            if (overScroller != null && !overScroller.isFinished()) {
                overScroller.abortAnimation();
            }
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
    }

    @Override
    public boolean onStartNestedScroll(CoordinatorLayout parent, AppBarLayout child, View directTargetChild, View target, int nestedScrollAxes, int type) {
        stopAppbarLayoutFling(child);
        return super.onStartNestedScroll(parent, child, directTargetChild, target, nestedScrollAxes, type);
    }

    @Override
    public void onNestedPreScroll(CoordinatorLayout coordinatorLayout, AppBarLayout child, View target, int dx, int dy, int[] consumed, int type) {
        //type返回1时，表示当前target处于非touch的滑动，
        //该bug的引起是因为appbar在滑动时，CoordinatorLayout内的实现NestedScrollingChild2接口的滑动子类还未结束其自身的fling
        //所以这里监听子类的非touch时的滑动，然后block掉滑动事件传递给AppBarLayout
        if (type == TYPE_FLING) {
            isFlinging = true;
        }
        if (!shouldBlockNestedScroll) {
            super.onNestedPreScroll(coordinatorLayout, child, target, dx, dy, consumed, type);
        }
    }

    @Override
    public void onNestedScroll(CoordinatorLayout coordinatorLayout, AppBarLayout child, View target, int dxConsumed, int dyConsumed, int
            dxUnconsumed, int dyUnconsumed, int type) {
        if (!shouldBlockNestedScroll) {
            super.onNestedScroll(coordinatorLayout, child, target, dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed, type);
        }
    }

    @Override
    public void onStopNestedScroll(CoordinatorLayout coordinatorLayout, AppBarLayout abl, View target, int type) {
        super.onStopNestedScroll(coordinatorLayout, abl, target, type);
        isFlinging = false;
        shouldBlockNestedScroll = false;
    }
}
